As stated by `man terminator_config`:
dbus: Control whether or not Terminator will load its DBus server. [...] If this configuration item is set to False, or the python dbus module is unavailable, running Terminator multiple times will run a separate Terminator process for each invocation.
I can confirm that after emerging dev-python/dbus-python, enabling the "dbus server" option in Terminator works as intended, and only only one Terminator process is spawned.
For now, in the terminator ebuild: dbus? ( sys-apps/dbus )
I guess it should be: